| dc.description.abstract | Scanning acoustic microscopy (SAM) and photoacoustic microscopy (PAM) techniques have been attracting attention over the past few decades because of their non-invasive and non-ionizing nature. However, current desk-top SAM and PAM systems utilizing mechanical stages are usually bulky and thus difficult to be miniaturized as hand-held or endoscopic probes. In recent years, MEMS (microelectromechanical system) technology has been applied to develop other optical microscopy systems: confocal microscopy and optical coherent microscopy. However, these MEMS devices are not suitable for SAM or PAM systems because liquid environment is necessary for ultrasound propagation. The work in this dissertation focuses on the development of reliable water-immersible scanning mirrors with polymer torsional hinges using micromachining technology. First, a new water- -immersible two-axis scanning mirror driven by multiple actuators is proposed and prototype is fabricated. The prototype is able to provide predictable, reliable and repeatable raster scanning pattern in both air and water. Second, combining 3D printing mounting structures, a miniaturized single-axis scanning mirror driven by single actuator is fabricated and characterized. Furthermore, in order to miniaturize the package size of the water-immersible two-axis scanning mirror, innovations have been made from both designing principle and fabrication technique perspectives. In the third prototype, it is possible to achieve two-axis scanning with single actuator through dynamic filtering principle. Therefore, the package size and module complexity can be reduced. Lastly, a high resolution polymer fabrication recipe is developed for the fourth prototype. With high structural resolution, the overall package size is reduced from 16 × 16 × 13 mm^3 to 5 × 5 × 5 mm^3 . At the same time, since the fabrication process is based on common MEMS treatment methods and minimal manual assemble involved, it is possible to batch fabricate this prototype, further reducing the cost of each piece. | |
